The present invention relates to an occupant sensor for identifying the category of the human being and the child restraint system loaded on the seat of a passenger vehicle.
An airbag apparatus is normally provided in the passenger vehicle for protecting occupants in case of accident such as a collision. The airbag is controlled in such a manner that when the occupant is a child or an infant seated on the child restraint system, the airbag is deployed softly or even not deployed.
In order to perform such a control, it is necessary to judge whether the human being loaded on the seat is an adult or a child, and whether it is a human being or a child restraint system. Hitherto, such method that the weight of the object loaded on the seat is weighed first, and then the category of the occupant and the existence of the child restraint system are judged has been employed in order to achieve this object; for example, a method for installing a load sensor under the seat for measuring the weight of the object loaded on the seat, and judging the object loaded on the seat as being an adult when the weight is not less than a predetermined value (for example 30 kg), and as being a child or a child restraint system when it is less than the predetermined value.
However, the method described above has a following problem. As one of the methods for fixing a child restraint system on the seat, there is a method of fixing it by using a seatbelt. In this case, since the seatbelt fixes the child restraint system with a strong force, a tensile force on the seatbelt is applied to the load sensor, and thus there is a possibility where a larger load than the actual load of the child restraint system loaded thereon would be detected be the load sensor. In such a case, the object loaded on the seat may be misjudged as being an adult even when an infant is seated on the child restraint system.
With such a circumstance in view, the object of the present invention is to provide an occupant sensor in which the misjudgment by the possible influence of a tensile force on the seatbelt described above can be prevented, and whether the object on the seat is a child restraint system or an adult can be identified reliably even when the child restraint system is fixed by the seatbelt.
According to a first embodiment of the present invention, an occupant sensor for identifying the category of an occupant and the presence of a child restraint system on a seat of a passenger vehicle is provided. The occupant sensor comprises a seat load sensor for detecting the weight of the occupant seated on the seat or the object loaded on the seat, and a seatbelt extraction amount sensor for detecting the extracting amount of the seat belt is not less than a predetermined amount. The sensor is configured so that (1) when the detected signal of the seatbelt extraction amount sensor is ON, the object loaded on the seat is judged as being a child restraint system irrespective of the value of the seat load sensor; and (2) when the detected signal of the seatbelt extraction amount sensor is OFF, (a) when the value from the seat load sensor is less than a predetermined value, the object loaded on the seat is judged as being a child restraint system or a child; and (b) when the value from the seat load sensor is not less than the predetermined value, the object loaded on the seat is judged as being an adult.
In this measure, by providing a seatbelt extraction amount sensor that is turned on when the full amount of seatbelt is unwound, and judging the object loaded on the seat as being a child restraint system when the sensor is turned ON irrespective of the output of the seat load sensor, identification between a state in which a child restraint system is loaded and a state in which an adult is seated can be made.
When the seatbelt extraction amount sensor is OFF, the object loaded on the seat should simply be judged as being a child restraint system or a child when the value from the seat load sensor is less than a predetermined value, and that an adult is seated when the value from the seat load sensor is not less than the predetermined value.
The seatbelt extraction amount sensor can be easily realized, for example, by mounting a rotary encoder on the spool of the seatbelt retractor device and judging whether the seat belt is unwound by a predetermined amount according to the output thereof.
Employing the full amount of the seat belt as the predetermined amount, or allowing the sensor to be actuated when the full amount of the seatbelt is unwound eliminates misjudgment of an adult with large physic on the seat as being a child restraint system. The same thing can be said for the seatbelt extraction amount sensor for other means.
According to a second embodiment of the invention, an occupant sensor for identifying the category of an occupant and the presence of a child restraint system on the seat of a passenger vehicle is provided. The occupant sensor comprises: a seat load sensor for detecting the weight of the occupant seated on the seat or the object loaded on the seat, and a seatbelt extraction amount sensor for detecting the extracting amount of the seat belt is not less than a predetermined amount; wherein
(a) when the value from the seat load sensor is less than a predetermined value, the object loaded on the seat is judged as being a child restraint system or a child. The sensor is configured so that: (b) when the value from the seat load sensor is not less than the predetermined value, the object loaded on the seat is judged as being an adult; and wherein when the detected signal from the seatbelt extraction amount sensor is ON, the predetermined value is set to the larger value than the case where it is OFF.
According to the second embodiment, when an adult with an extraordinarily large physic is seated, the detected signal from the seatbelt extraction amount sensor may be turned ON since a large amount of seatbelt is unwound, whereby the object loaded on the seat may be misjudged as being a child restraint system. In this measure, the basic method of judgment is that when the value from the seat load sensor is less than a predetermined value, the object loaded on the seat is judged as being a child restraint system or a child, and when the value from the seat load sensor is not less than the predetermined value, the object loaded on the seat is judged as being an adult. When the detected signal from the seatbelt extraction amount sensor is ON, the predetermined value, which is a threshold value, is set to the larger value than in the case where it is OFF.
The larger value should simply be set to the value larger than the value detected by the seat load sensor when a child restraint system is fixed on a seat by a seatbelt and an infant is seated thereon. This eliminates misjudgment of the object loaded on the seat as being a child restraint system when an adult with extraordinarily large physic is seated, and an adult is reliably differentiated from a child restraint system.
According to a third embodiment of the invention, an occupant sensor arranged as in the first and second embodiments mentioned above, may further comprise a buckle switch for detecting engagement between a buckle and a tongue of the seat belt, wherein the ON signal from the seatbelt extraction amount sensor is considered to be effective only when the signal from the buckle switch is ON.
The seatbelt is normally brought into a fastened state by engaging a tongue, that a seat belt is inserted into, with the buckle fixed to the buckle anchor. In this case, it is a buckle switch that detects whether the tongue is in engagement with the buckle and supplies a signal that is turned ON when they are in engagement, which is well known.
In the third embodiment, since the ON signal from the seatbelt extraction amount sensor is effective only when the signal from the buckle switch is ON, the sensor does not judge the object loaded on the seat as being a child restraint system when the seatbelt is unwound without being fastened.
According to a fourth embodiment of the present invention, an occupant sensor is provided. The sensor configured as described in any of the three embodiments mentioned above further arranged so that the seatbelt extraction amount sensor is integrated into a locking mechanism of an ALR retractor or an ELR retractor with ALR switch function.
The ALR retractor is one of the seatbelt retracting devices, and is also called as an automatic locking safety belt retractor. This is constructed in such a manner that when a predetermined amount of seatbelt is unwound, the rotation of the winding mechanism in the direction in which the seatbelt is unwound is locked and thus further unwinding operation is prevented while allowing only winding operation. The ELR retractor with ALR switch function is for example the one disclosed in Japanese Examined Utility Model Publication No. 4-15557 (incorporated by reference herein in its entirety), which is constructed in such a manner that it works as a normal emergency locking safety belt retractor (ELR) until the seatbelt is unwound by a predetermined amount, and when the seat belt is unwound by a predetermined amount, it works as an ALR retractor.
Both types of the seatbelt retractor have a mechanism for detecting that the seatbelt is unwound by a predetermined amount (normally full amount or near full amount) and for locking further unwinding operation thereof. Therefore, by providing a limit switch to the locking mechanism and using it as a seatbelt extraction amount sensor, the mechanism of the seatbelt extraction amount sensor can be simplified.
According to a fifth embodiment of the present invention, an occupant sensor is provided. The sensor is arranged according to any one of the first to third embodiments mentioned above and is configured so that the seatbelt extraction amount sensor is an ALR switch sensor of the ELR retractor with ALR switch function.
The ELR retractor with ALR switch function works as an normal emergency locking safety belt retractor (ELR) till the seatbelt is unwound by a predetermined amount, and works as an automatic locking safety belt retractor (ALR) once the seatbelt is unwound by a predetermined amount. In this ALR state, further unwinding operation is locked and only winding operation is possible. In case an ALR switch sensor for detecting that the seatbelt is unwound by the predetermined amount is employed, the sensor can be used as a seatbelt extraction amount sensor, even if no particular extraction amount sensor is employed.
It is to be understood that both the foregoing general description and embodiments mentioned above and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.